For the skeletal chassis of very-lengthily longitudinally extending motor-home roadway vehicles, the primary and major weight-bearing capability has been traditionally provided by two or more longitudinally extending, parallel channel-type structural members that respectively extend along the entire chassis length. Because such traditional prior art structure provides numerous constraints for designers of motor-home vehicles, it is the general objective of the present invention to radically depart from these traditional chassis constraints to thereby open numerous ancillary vistas including, inter alia, capability through a single central elongate structural member for providing chassis torsional rigidity, capability for accommodating longitudinal utility and/or control conduits therewithin, and the capability therebelow for furnishing unusually transversely lengthly and longitudinally consecutive storage compartments.